Structural Stabilities of Ordered Arrays of Nb₄ Clusters on NaCl(100) Surface

Adsorption of ordered (2×2) arrays of Nb₄ clusters on the insulating surface of NaCl(100) is studied by the first-principles calculations within the density functional theory. The calculations on the relaxed geometries and cohesive energies show that both the tetrahedron and quadrangle-Nb₄ can be stably adsorbed on this substrate, which may have important applications. The adsorption of quadrangle-Nb₄ on the NaCl(100) surface is more stable than that of tetrahedron-Nb₄. Both the Nb₄ clusters studied and a single Nb atom prefer the top site of the Cl atom in the NaCl(100) surface. Electronic structure analysis suggests that the interactions between the Nb₄ clusters and the substrate are weak